1. Field of the Invention
The present invention relates to a reinforced polypropylene resin composition which has a light weight, excellent rigidity, heat distortion resistance and impact resistance, and which permits the formation of a large molded product having excellent dimensional stability and appearance in a short molding cycle. The reinforced polypropylene resin composition of the present invention is suitably used in the field of large automobile parts such as an instrument panel and so on.
2. Description of the Related Art
Traditionally, a reinforced polypropylene resin composition comprising a polypropylene resin as a main component in combination with thermoplastic elastomer and an inorganic filler was generally used for automobile parts within a wide range. The required heat distortion resistance, impact resistance, dimensional stability and moldability of the reinforced polypropylene resin composition increase in level with expansion of the field of the application thereof. Investigation was thus made for improving the properties by variously changing the polypropylene resin, thermoplastic elastomer and inorganic filler, which are contained in the reinforced polypropylene resin composition.
An example of such a reinforced polypropylene resin composition is a combination of a crystalline ethylene-propylene block copolymer having a specified ethylene content, MFR, p-xylene soluble content and intrinsic viscosity, ethylene-propylene copolymer rubber and inorganic filler having a specified average particle size (Japanese Patent Laid-Open No. 58-168649). Investigation was also made of a reinforced polypropylene resin composition comprising a combination of a crystalline ethylene-propylene block copolymer, a hydrogenated block copolymer rubber, ethylene-propylene copolymer rubber having a specified molecular structure and MFR, and an inorganic filler such as talc or the like (Japanese Patent Laid-Open Nos. 3-172339 and 61-291247). Various examinations were performed for the particle size, particle distribution, etc. of the talc added (Japanese Patent Laid-Open Nos. 63-150343 and 4-57848).
However, in recent automobiles, since the room temperature is easily increased due to the small inclination angle of the window glass, the demand for the heat distortion resistance of an instrument panel, etc is increased. On the other hand, the importance of light weight, improvement in the appearance and reduction in the molding time are also increased. However, previous proposed materials are difficult to comply with these demands over a wide range.
The present invention has been achieved in consideration of the above situation, and an object of the invention is to provide a reinforced polypropylene resin composition which can satisfy the above various requirements.